The present invention relates to subterranean treatment operations. More particularly, the present invention provides methods that may be useful in providing void-free barriers between a subterranean formation and a portion of a well bore.
Hydrocarbon production from subterranean formations commonly involves, inter alia, drilling a well bore that penetrates the hydrocarbon-bearing formation, and producing hydrocarbon fluids (e.g., oil and/or gas) through the well bore to the surface. When the formation is one that may be characterized as poorly or weakly consolidated, efficient hydrocarbon production may be complicated by, inter alia, well bore instability and the production of “fines” from the formation. Production of fines (e.g., particles from the formation) along with the produced fluids is undesirable, as they may damage both downhole equipment and surface equipment, and must be disposed of in an environmentally-acceptable manner.
Conventional attempts to address the problems of well bore instability and formation fines production have involved operations referred to as “gravel packing.” Commonly, a gravel packing operation may involve placing a sand slurry into an annulus between a screen-wrapped perforated pipe (the “screen”) and the walls of the well bore, thereby forming a sand filter between the two. The sand (often referred to as “gravel”) may be of a specific size designed to prevent the passage of unconsolidated formation particles. A wide range of sizes and screen configurations are available to suit the characteristics of the gravel pack sand used. Similarly, a wide range of sizes of gravel is available to suit the characteristics of the unconsolidated or poorly consolidated particulates in the subterranean formation. The resulting structure presents a barrier to migrating formation particles, and stabilizes the weak formation, while still permitting fluid flow. The gravel, inter alia, acts to prevent the particulates from occluding the screen or migrating with the produced fluids, and the screen, inter alia, acts to prevent the gravel from entering the production tubing.
Occasionally, expandable screens have been placed in subterranean formations as an alternative to the placement of a conventional gravel pack. Once placed within the well bore, the expandable screen may be expanded or inflated against the walls of the well bore.
Conventional gravel packing operations, as well as operations involving the use of expandable screens, have been problematic. Bridging of sand particles within the gravel pack may occur, which may create voids within the gravel pack. Void spaces also may occur with expandable screens. When a well bore is drilled in a soft formation, formation material may be washed out in certain locations, which may enlarge the diameter of the bore hole in the washed-out regions. Generally, expandable screens are expanded through the use of a fixed-diameter die. Accordingly, in a uniform-diameter borehole, the expanded screen generally will make contact with substantially the entirety of the formation, and be void-free. However, in locations that have been washed out to a larger diameter, or into an irregular shape, the expanded screen will be unable to contact substantially the entirety of the formation, and voids will be present.
The presence of voids generally is undesirable, as they may result in mechanical failures, among other things. Generally, voids will reduce the ability of an expanded screen or gravel pack to filter or restrain particles or fines produced from the subterranean formation along with produced fluids. Fines may damage both downhole and surface equipment, due in part to the relatively high velocity with which fluids carrying the fines may move through the gravel pack or screen. For example, particles carried along with produced fluid may impinge on the expandable screen, abrading a hole therein. Furthermore, any produced formation material must be disposed of in an environmentally-acceptable manner, which adds expense to the cost of producing the well.